The present application seeks funding to establish an Intellectual and Developmental Disabilities Research Center (IDDRC) at the University of California, which will be fully integrated into, and benefit from, the existing resources of the UC Davis MIND Institute and its campus partners. The MIND Institute is an integrated program that is internationally recognized for ground-breaking studies of autism, fragile X syndrome, and other IDD conditions. The proposed IDDRC includes three components. First, we propose a research component that addresses the focus area of Multi-Modal Treatment Approaches. This component includes a clinical trial targeting children with fragile X syndrome that combines a drug (lovastatin) with a parent-implemented intervention. Novel outcome measures focusing on language and challenging behavior will evaluate efficacy. The clinical trial will be accompanied by studies focused on FMRI-related signaling pathways so as to illuminate the mechanisms by which treatment achieves its effects and to identify biomarkers that indicate treatment efficacy and individual differences in response to treatment. Second, we propose for inclusion 56 IDD-related projects funded by NIH and other federal and private sources. Ten of the projects are funded by NICHD. These projects address three scientific themes: Integrated Biobehavioral Characterization of IDD, Environmental Contributions to IDD, and Treatments for IDD. Third, we propose core components to facilitate interdisciplinary, translational research in IDD. The cores include an Administrative Core and a Clinical Translational Core, with the latter focused on recruitment and diagnostic characterization of human participants. The remaining cores will provide assays of immune function, cellular and molecular biology and imaging, and environmental contaminants (Biological Analysis Core); measures of complex human behavior, particularly for establishing endophenotypes (Neurobehavioral Analysis Core); assays of rodent behavior for evaluating mutant rodent models and supporting preclinical evaluations of drug safety and efficacy (Rodent Behavior Core); and the management and analysis of complex multidimensional data derived from human and animal studies (Biostatistics, Bioinformatics, and Research Design).